Brosol/Solex Main Jets 137.5

OVERVIEW

Precision fuel delivery is the lifeblood of any air-cooled Volkswagen engine, and these EMPI Brosol/Solex Main Jets in size 137.5 are the key to unlocking optimal performance and engine longevity. Whether you are running a stock 1600cc dual-port or a mildly modified street engine, the main jet dictates the air-to-fuel ratio during the most critical phases of operation. A 137.5 jet is often the perfect solution for enthusiasts dealing with the "lean" conditions common in modern ethanol-blended fuels or for those who have added a high-flow exhaust system. At Appletree Automotive, we know that a fraction of a millimeter can be the difference between a crisp-throttled cruiser and an engine that suffers from dangerous overheating due to a lean burn. These precision-machined brass jets ensure that your Solex or Brosol carburetor provides the exact metered fuel flow required to keep your flat-four running cool and strong.

Upgrading or replacing your main jets is one of the most cost-effective ways to tune your VW for specific driving conditions, altitudes, or engine configurations. These jets are designed to fit seamlessly into the standard jet carrier of Solex PICT series carburetors and their Brosol counterparts, offering a factory-level fit with aftermarket performance flexibility. When you are chasing that perfect tan color on your spark plugs, having a range of jets like the 137.5 allows for the fine-tuning necessary to eliminate flat spots and hesitation during acceleration. Don''t settle for a "one size fits all" approach to your fuel system; trust the specialists who live and breathe air-cooled technology to provide the components that keep your Beetle, Bus, or Ghia on the road for another generation. These jets represent the intersection of classic engineering and modern manufacturing precision, ensuring your carburetor performs exactly as intended by the German engineers of yesteryear.

FITMENT

• Volkswagen Type 1 Beetle: 1950-1979 (equipped with Solex or Brosol Carburetors)
• Volkswagen Type 2 Bus / Transporter: 1950-1971 (1200cc, 1500cc, and 1600cc upright engines)
• Volkswagen Karmann Ghia: 1956-1974
• Volkswagen Type 3 (Squareback, Fastback, Notchback): 1961-1973 (single or dual Solex applications)
• Volkswagen Thing (Type 181): 1973-1974
• Carburetor Compatibility: Solex 28 PICT, 30 PICT, 31 PICT, 34 PICT-3, 34 PICT-4, and Brosol H40/44EIS models.

SPECS

• Part Number: 43-5137-7
• Jet Size: 137.5 (Metric sizing)
• Material: High-Quality Precision Machined Brass
• Thread Type: Standard Solex/Brosol Main Jet Thread
• Quantity: Sold Individually (Each)
• Manufacturer: EMPI
• Application: Internal Carburetor Fuel Metering

PRO TIPS

Tip 1: Identifying the Lean Stumble

If your VW experiences a "flat spot" or a momentary hesitation when you transition from idle to mid-range throttle, it is often a sign of a lean condition. While many adjust the accelerator pump, the main jet plays a massive role in the transition circuit. Stepping up to a 137.5 main jet from a stock 127.5 or 130 can often eliminate this stumble, especially if you are running a 009 distributor which lacks vacuum advance. Always ensure your timing is set correctly before changing jets, as ignition issues can often mimic carburation problems.

Tip 2: Altitude and Environment Tuning

Remember that air density changes with altitude and temperature. If you live at sea level or in a very cold climate, your engine requires more fuel to maintain the correct ratio because the air is denser. A 137.5 jet is an excellent "winter" jet or sea-level jet for 1600cc engines that feel sluggish. Conversely, if you are heading into high-altitude mountain passes, you might find this jet too rich. Keep a log of your spark plug colorsyou are looking for a light toasted-marshmallow tan. If the plugs are white, you are lean; if they are sooty black, you are too rich.

Tip 3: Proper Installation and Sealing

When installing your new Brosol/Solex main jet, cleanliness is paramount. Even a microscopic piece of lint or a tiny grain of sand can clog the precision-drilled orifice of a 137.5 jet, causing your engine to sputter or die. Use a high-quality, properly fitting flathead screwdriver to seat the jet. Do not over-tighten, as brass is a soft metal and can easily deform or strip. Ensure the copper crush washer on the jet carrier plug is in good condition to prevent external fuel leaks, which are a major fire hazard in the air-cooled VW engine bay.